Ok, I understand. I'm didn't managed to screw myself up, I think. Flex is not an issue for a beginner like me.
Board length 151cm is fine for me to train on, but I should get a longer board in 1 to 2 years time. 154cm - 156cm would be the correct length.
Also, I should start hitting the running tracks to reduce weight.
Nobody said anything about the boots/bindings/board being different style, so I guess it's a non-issue.
Thanks for the help!